The invention is based on a device for and a method of detecting the backward revolution of a revolving component of an internal combustion engine of the generic type of the main claim, with which invention in particular the stalling of the internal combustion engine is to be detected.
In multicylinder internal combustion engines with electronically controlled injection, it is usually calculated in the control unit when and how much fuel is to be injected into which cylinder. So that these calculations can proceed in a correct way, the respective position of the crankshaft or camshaft of the internal combustion engine is to be detected; it is therefore usual, and is described for example in EP-PS 0 017 933, that the crankshaft or the camshaft is connected to a disk on whose surface at least one reference mark is provided, additionally a plurality of marks of the same kind, also referred to as increments, being provided on the crankshaft disk. These two revolving disks are sensed by appropriate, fixed sensors, an unambiguous indication of the position of crankshaft and camshaft is acquired in the control unit from the chronological sequence of the pulses supplied by the sensors, and corresponding actuation signals for the injection or ignition are formed in the control unit.
In order to ensure that the correct position of the crankshaft or camshaft is present, a synchronization must be carried out after the internal combustion engine is switched on. This takes place on the basis of the detection of the reference mark. During the operation of the internal combustion engine, a reset, which then leads to resynchronization, is usually triggered when the speed of revolution of the control unit drops below a minimum value.
Under unfavorable circumstances, for example if the internal combustion engine, or the engine, stalls, the engine may revolve backward. usually, when such backward revolution of the engine takes place the dropping of the speed of revolution below a minimum value is not detected. Then, a reset normally takes place at the next synchronization point since a synchronization fault is detected by the control unit. If at the point of backward revolution it is detected that the speed of revolution drops below a minimum value, a reset usually takes place immediately. However, in both cases resynchronization takes place again immediately after the reset has occurred, and since the backward revolution is not detected, injection and ignition start when the engine is still revolving backward. These ignitions then take place at the wrong time since the control unit assumes the engine is revolving in the correct direction and, furthermore, with constant spark distribution the ignitions also take place in the wrong cylinder.
In this case, the exhaust gases, and noncombusted fuel mixture, are pushed back into the intake manifold of the internal combustion engine. In unfavorable cases, combustions can lead to the engine accelerating in the backward direction of revolution, or combustions may continue as far as the intake manifold. This problem is known under the term backfiring. Such combustions can cause damage in the intake manifold of the internal combustion engine due to the occurrence of excess pressure.